A Latin American Perspective to Agricultural Ethics

The mixture of political, social, cultural and economic environments in Latin America, together with the enormous diversity in climates, natural habitats and biological resources the continent offers, make the ethical assessment of agricultural policies extremely difficult. Yet the experience gained while addressing the contemporary challenges the region faces, such as rapid urbanization, loss of culinary and crop diversity, extreme inequality, disappearing farming styles, water and land grabs, malnutrition and the restoration of the rule of law and social peace, can be of great value to other regions in similar latitudes, development processes and social problems. This chapter will provide a brief overview of these challenges from the perspective of a continent that is exposed to the consequences of extreme inequality in multiple dimensions and conclude by arguing for the need to have a continuous South-South dialogue on the challenges of establishing socially and environmentally sustainable food systems

The development of endomycorrhizal root systems VIII. Effects of soil phosphorus and fungal colonization on the concentration of soluble carbohydrates in roots

Concentrations of phosphorus in shoot and soluble carbohydrates (fructose, glucose, sucrose and fructans) in root were measured in non-mycorrhizal and vesicular-arbuscular (VA) mycorrhizal (Glomus mosseae) leek plants (Allium porrum) raised at six concentrations of soil phosphate. In conditions when an increased concentration of soil phosphate reduced VA mycorrhizal infection, the concentrations of soluble carbohydrates in the root were at a maximum. Therefore the hypothesis that greater concentrations of soluble carbohydrates in roots favour VA mycorrhizal infection is discounted. There was a specific effect of VA mycorrhizas, in that infected roots contained a larger concentration of sucrose than did uninfected roots, in plants with similar phosphorus concentrations in dry matter of shoots. We conclude, first, that increased phosphorus supply from either phosphate addition to soil or VA mycorrhizal infection increases concentration of soluble carbohydrates in leek roots and, secondly, that the VA mycorrhizal root behaves as a particularly strong physiological sink when there is an excess concentration of sucrose in the host

Mathematical modelling of cancer cell invasion of tissue: the role of the urokinase plasminogen activation system

The growth of solid tumours proceeds through two distinct phases: the avascular and the vascular phase. It is during the latter stage that the insidious process of cancer invasion of peritumoral tissue can and does take place. Vascular tumours grow rapidly allowing the cancer cells to establish a new colony in distant organs, a process that is known as metastasis. The progression from a single, primary tumour to multiple tumours in distant sites throughout the body is known as the metastatic cascade. This is a multistep process that first involves the over-expression by the cancer cells of proteolytic enzyme activity, such as the urokinase-type plasminogen activator (uPA) and matrix metalloproteinases (MMPs). uPA itself initiates the activation of an enzymatic cascade that primarily involves the activation of plasminogen and subsequently its matrix degrading protein plasmin. Degradation of the matrix then enables the cancer cells to migrate through the tissue and subsequently to spread to secondary sites in the body. In this paper we consider a mathematical model of cancer cell invasion of tissue (extracellular matrix) which focuses on the role of the plasminogen activation system. The model consists of a system of reaction-diffusion-taxis partial differential equations describing the interactions between cancer cells, urokinase plasminogen activator (uPA), uPA inhibitors, plasmin and the host tissue. The focus of the modelling is on the spatio-temporal dynamics of the uPA system and how this influences the migratory properties of the cancer cells through random motility, chemotaxis and haptotaxis. The results obtained from numerical computations carried out on the model equations produce rich, dynamic heterogeneous spatio-temporal solutions and demonstrate the ability of rather simple models to produce complicated dynamics, all of which are associated with tumour heterogeneity and cancer cell progression and invasion

Total occlusion of the left main coronary artery with preserved left ventricular function

Two patients with total occlusion of the left main coronary artery and well preserved left ventricular function are reported. Twenty one similar cases have been reported in the world literature. All the patients had angina pectoris. Twenty one of the 23 patients (including our cases) underwent coronary artery bypass graft surgery while the other two received medical treatment. All are alive for a follow-up period of 0.4-67 months. It is concluded that in patients with chronic total occlusion of the left main coronary artery and well preserved left ventricular function, collateral flow is always extensive but insufficient to prevent angina. Functional status is greatly improved by surgery, although survival is excellent in both treated and non-treated surgically patients. (C) 1997 Elsevier Science Ireland Ltd